Description

Models to predict energy expenditure from CSA accelerometer counts/min and/or heart rate were created in a sample of 12 males using individual and group calibration approaches. Percent error for each model was: CSA only (individual calibration: -50.8, group calibration: -45.1), heart rate only (individual calibration: 39.1, group calibration: 48.8), non-branched CSA plus heart rate (individual calibration: 29.9, group calibration: 25.7), branched CSA plus heart rate using a priori parameters, (individual calibration: -4.4, group calibration: 3.5) branched CSA plus heart rate using post hoc parameters (individual calibration: -1.5, group calibration: 0.1).

Development/Validation

Sample: 12 males, 22.7-30.0 years of age

Setting: Laboratory

Activities: Activities of daily living, cycling, stationary, stepping, treadmill walking and running

Criterion: EO Sprint by Jaeger (VO₂), heat sink calorimeter

Accelerometer(s): CSA on each hip

Validation approach: Comparison to criterion

Phase Designation

(What's this?)

This model is in Phase 0, 1, and 2.

Instructions

Multiple models were created- CSA only, heart rate only, non-branched CSA plus heart rate, branched CSA plus heart rate with parameters determined a priori, branched CSA plus heart rate with parameters determined post hoc, each using group and individual calibration. Physical activity intensity (PAI) is reported in kilojoules per kilogram per minute by and defined as VO₂ minus measured RMR. Heart rate is expressed as beats/minute above resting heart rate. CSA is the mean accelerometer values per minute.

CSA only

The flex point was defined as 50% of the mean CSA output at 3 km/h. At the group level, this value was 497 counts/min. Above the flex point, PAI is predicted from the equation 0.053*CSA + 47.88. Below the flex point, PAI is calculated as 0.15*CSA.

Heart rate only

The flex heart rate was defined as 10 beats/min plus the average of resting heart rate and the mean heart rate at 3 km/h. Below this flex heart rate, PAI is 0 kJ/kg/min. Above flex heart rate, PAI is predicted from the equation 0.011*heart rate² + 5.82*heart rate.

Non-branched CSA plus heart rate

PAI is predicted using the equation 0.028*CSA + 4.04*heart rate

Branched CSA plus heart rate

Branched models follow the following flow chart and used either a priori parameters or post hoc parameters which are found below.

Using a priori parameters

y= walking/running transition heart rate (mean heart rate between fastest walking and slowest running speed)

z= flex heart rate (10 beats/min plus the average of resting heart rate and the mean heart rate at 3 km/h)

P1=100%

P2=P3=50%

P4=0%

x=5 counts/min

Using post hoc parameters

Parameters are found in the table below.

Source Information

Reference:

Brage, S., Brage, N., Franks, P. W., Ekelund, U., Wong, M. Y., Andersen, L. B., ... & Wareham, N. J. (2004). Branched equation modeling of simultaneous accelerometry and heart rate monitoring improves estimate of directly measured physical activity energy expenditure. Journal of Applied Physiology. https://doi.org/10.1152/japplphysiol.00703.2003 Link to Paper

Corresponding author: Søren Brage, sb400@medschl.cam.ac.uk

Contact

Kimberly Clevenger at accelerometerrepository@gmail.com